This invention relates to attitude sensors for determining attitude information for an orbiting body, and more particularly, to a sun sensor for sensing the position of an orbiting body using an analog sun sensor in the form of a continuous sensor which is periodically updated by a patterned mask, periodic analog sun sensor that creates one or more narrow fields of view for detecting the sun as it passes therethrough, thereby precisely providing the position of the sun at a given time which is used to correct the position provided by the continuous sensor.
Attitude sensors are devices mounted on an orbiting body such as satellites, missiles, space probes, extremely high flying aircraft and the like which sense a reference body and produce a signal which indicates orientation of the orbiting body with respect to the reference body. The attitude of the orbiting body, which generally orbits the earth, is determined by its position with respect to three axes at right angles to each other, two of which are in a plane at right angles to a projected radius of the earth passing through the orbiting body which plane is parallel to the earth's horizon. Conical scan horizon sensors are frequently used in spacecraft to determine pitch and roll attitude by sensing the position of the earth's horizon in several directions. The third axis called yaw is an attitude around an axis through the center of the earth which cannot be obtained from the horizon data, and accordingly, observations of some other celestial body or object, usually the sun, are required.
Sun sensors for providing yaw used on spacecraft generally fall into two categories, one being analog devices which are typically low cost and low precision. The second being digital devices which are typically high cost and high precision, but are generally complex and require additional weight and power which are undesirable features.